Impression tray and method of making dentures



Feb. 8, 1944. s. MYERSON 2,341,155

IMPRESSION TRAY AND METHOD OF MAKING DENTURES Filed NOV. 20, 1940 Patented Feb. 8, 1944 UNITED STATES PATENT OFFICE IMPRESSION TRAY AND METHOD OF MAKING DENTURES 12 Claims.

This invention pertains to the art of dentistry, and relates more particularly to an improved impression tray and to an improved method of making dentures.

In the usual practice of denture making, a socalled impression tray of metal is employed for holding the body of plaster or the like against the surface of the oral cavity while taking the impression, the tray forming a rigid support against which the dentist may exert the desired amount of pressure by means of his finger tips, thus insuring a sharp impression and holding the plastic material in position while it is setting. Such trays are usually of sheet metal and are furnished in a substantial range of sizes. After the impression has been taken, a plaster model is made which exactly follows the contour of the impression and which is employed in making up the wax-bite, trial plate, and in performing other usual operations preliminary to completion of the denture. However, it is to be observed that until all of these preliminary steps, usually involving several visits of the patient to the dentists office, have been taken, no opportunity is given to determine the appearance of the teeth and denture in the patients mouth, or actually to test the functional accuracy of the teeth.

The present invention has for one of its principal objects the provision of an improved method of making dentures and a novel impression tray designed to be used in the practice of such method, whereby both dentist and patient are enabled, at the patients very first visit, to observe the visual and functional effect of the teeth which are actually to be employed in the completed denture just as they will be arranged in the mouth when the denture is complete. Thus at the earliest stage of the process, the teeth may be tested individually and collectively for size, shape, color and function while actually positioned in the patient's mouth as they will be in the completed denture. The present invention also makes it possible at this early stage to arrange the teeth in any desired manner, with ease and accuracy and without discomfort to the patient and at a great saving of time and cost. It is thereby possible to secure the patients approval of the appearance and to check up on the function of the denture that is to be made, at the very first stage in the procedure-in fact at the very first visit.

A further object is to provide an improved so 'as readily to accommodate it to different mouth contours. A further object is to provide an impression tray having provision for removably holding a plurality of teeth therein in such a way as to permit interchange and adjustment of the teeth and also having provision for simulating the gum tissue in which the necks of natural teeth are embedded. A further object is to provide an improved tray of such a nature that by its use certain of the usual steps in denture making may be eliminated. To this end the tray may be of a thermoplastic material which becomes sufficiently ductile or pliable at a temperature below that which would injure the mouth tissues to permit the dentist, by means of his finger tips, to mould it into approximate conformity with the surfaces of the oral cavity. Since the tray thus moulded approximately follows the contours of the oral surfaces, only a relatively small amount of impression material need be used, thus insuring a very perfect fit of the impression.

Another object is to provide a tray designed temporarily to receive the posterior teeth only but having provision for removably attaching it to a holder in which are mounted the anterior teeth.

Other objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawing, in which Fig. 1 is a perspective view of a dental impression tray according to one embodiment of the present invention;

Fig. 2 is a fragmentary section substantially on the line 2-2 of Fig. 1;

Fig. 3 is a perspective View of an impression tray designed to hold posterior teeth only;

Fig. 4 is a perspective view of a tooth holder carrying anterior teeth, and which may be combined with the tray of Fig. 3 to form a complete impression tray whose parts are relatively adjustable;

Fig. 5 is a vertical section showing posterior and anterior tray members held in assembled relation by means of a simple form of screw clamp;

Fig. 6 is a bottom view of an impression tray similar to that of Fig. 3 but provided with a different form of clamping means for adjustably attaching an anterior holder thereto;

Fig. 6 is a perspective view of the clamp of Fig. 6; a

Fig. 7 is a transverse section of an impression tray of modified construction in which the lateral portions are relatively adjustable;

Fig. 8 is a perspective view of a length of rope wax useful in removably securing teeth to the improved tray;

Fig. 9 is a perspective View of an impression tray for use in making a lower denture;

Fig. 10 is a section on the line Ill-H] of Fig. 9;

Fig. 11 is a diagrammatic transverse section through the hard palate of the mouth illustrating one step in the improved method of making dentures;

Fig. 11 is a view similar to Fig. 11 but illustrating a subsequent step in the process; and

Fig. 12 is a perspective view of a tool useful in removing the impression tray from the mouth.

Referring to the drawing, the numeral I designates one form of impression tray in accordance with the present invention, such tray being of a material which is normally rigid and shaperetaining, for example, metal, a cellulose derivative, vulcanite, or one of the synthetic resins. The tray shown in Fig. l is for use in making an upper denture, and its upper or impression surface is contoured to provide the U-shaped channel 2 for the reception of the upper gum ridgeand to provide the roof 3' which conforms more or less to the contour of the hard palate.

As particularly distinguishing from prior impression trays, this improved tray is provided at its lower side with a channel 4 for the reception of artificial teeth, such channel being of more or less U-shape in plan View, and having its labial wall 5 designed to simulate the gum tissue which surrounds the necks of natural teeth, the lower margin of this Wall 5 being formed into cusps 6 designed to extend partially around th necks of teeth whose gingival portions are disposed within the channel 4.

The tray, as illustrated in Fig. 1, is designed to take the place of and to perform the function of the usual impression trays now commonly employed. Such trays are usually provided in a range of sizes, which may include as many as thirty trays, and when the tray I is unitary and of a rigid material, such'as metal, vulcanite, or the like, a similar range of sizes will be provided.

In the use of this novel tray the dentist may, by repeated trial, select that one from the size range which most nearly approximates the contour of the surfaces of the upper or lower jaw to which the denture is, to be fitted.

Having selected the proper impression tray, a body of tooth-holding material, for example dental wax, is placed in the channel 4. Conveniently this wax may be provided in the form of a rope wax-strip W, as shown in Fig. 8, the wax or other waxy material being of a kind which melts at a low temperature but which when at normal temperatures is sufficiently stiff and retentive to hold the teeth in properly adjusted position. This tooth-holding material is preferably of a character such that it only becomes soft enough to permit adjustmentof the teeth therein when the wax has been warmed slightly. However, whatever the material employed, it is essential to the practice of the present invention that such material, though capable normally of retaining the teeth firmly in place, nevertheless, permits or may be made to permit relative adjustment or even removal of individual teeth without distorting 0r destroying the tray proper, or necessarily affecting the position of other teeth mounted in the tray.

Having provided the channel 4 with this body of wax or other tooth-holding material, the dentist then selects a set of teeth and embeds their gingival ends within the wax in the channel 4, so disposing the teeth that the cusps 6 of the wall 5 partially surround the necks of the several teeth. Having placed the teeth in a tentative arrangement in the tray, the dentist then places the tray in the patients mouth, and by observation determines whether the teeth have the proper appearance and are correct for size and form, and whether they are disposed in the proper relative orientation and inclination. He may also determine whether the teeth are correctly set up for function against opposite natural teeth, if such are present, or against opposed artificial teeth. As many of the teeth in the tray as may be necessary may now easily be ground or replaced with others, until finally the appearance and function of the teeth is what is most desirable. The impression tray is now removed from the mouth and a layer of plastic impression material, for example, plaster of Paris, or some of the special substances sold under well-known trade names, is placed upon the upper surface of the tray so as to line the channel 2 and to cover the roof 3. The tray is now placed in the patients mouth and held with the proper degree of pressure against the surface of the oral cavity until the impression layer has set. The tray is now removed from the patients mouth, this tray with its impression layer and teeth now constituting what may be termed a trial plate, the upper surface of which is contoured exactly to fit the patients mouth and which carries theset of teeth which are to be used in a permanent denture and which are of the color, shape, arrangement and location which has been found by test to give the optimum results. Since by this method the trial plate fits the patients mouth with the most extreme accuracy, it may be very difficult to remove it from the mouth merely by the use of the fingers. To facilitate such removal, the impression tray may b provided with one or more openings or recesses SI, and a tool 32 (Fig. 12) may be furnished, such tool having a hooked end 33, which may be hooked into the openings 3| to assist in loosening the tray from the oral surfaces.

a After surplus impression material has been removed, this accurately fitting trial tray ortrial plate is replaced in the mouth for exact checkup of the positions of the teeth for appearance and function. Adjustments may be easily and accurately made since this trial plate will stay in the mouth securely and in exact position. If the tray be thick or jointed, as shown, in some forms of this invention, then a wax bite should be taken before removing the impression tray and trial plate from the mouth.

In this case, the model is poured and the model preferably mounted on an articulator; the positions of the teeth. are accurately registered in plaster; the tray is removed; the teeth are smoothly waxed to the model; the model is invested, and the denture is completed in usual manner. It will be observed that after the accurate check-up and making the wax bite (which may readily be. done at the patients first visit), all subsequent steps may be carried out in the laboratory and do not require the further presence of the patient.

By; the procedure described it is possible-at an early stage in the making, of thedenture to determine exactly how the teeth will appear in the completed denture, and to determine much more accurately than has previously been possible, the functional, as well as the aesthetic, arrangement of the teeth at the very first visit.

While in Fig. 1 the impression tray is shown as consisting of a single piece of material integrally mounted or otherwise formed, it is contemplated that the tray may be made of a plurality of parts which may be so united as to permit relative adjustment, thus affording greater latitude in fitting the mouth with a given tray than when the tray is of a single piece, and reducing the number of trays necessary to cover the usual size-range.

Thus in Figs. 3 and 4 the tray I is shown as comprising a posterior portion having gum-receiving channels 8 at its opposite sides, and the roof portion 1 the upper surface of this posterior tray member constituting the impression surface. While the tray is shown as having the roof portion l this roof portion may be omitted if desired. The opposite side of the tray is provided with a groove at each side for the reception of the gingival ends of the teeth, the outer wall 9 of such groove being designed to simulate the gum tissue, and terminating at its lower margin in downwardly directed cusps Id designed to intervene between the necks of adjacent teeth ll. With this posterior portion 1 there may be associated an anterior portion I2 which, if desired, may be identical in all respects with the tooth holder disclosed in the copending application of Simon Myerson, Serial No. 313,077, filed January 9, 1940. Thus this anterior portion l2 may comprise the rigid supporting member 13 which may, for example, be of vulcanite, a synthetic resin, or the like, having its rear surface shaped to provide a channel for the reception of the anterior portion of the gum ridge, and having in its opposite side a channel whose labial wall M is designed to simulate the gum tissue, such channel being shaped to receive the gingival portions of anterior teeth It. This anterior impression tray or holder i2 is provided with an elongate rearwardly projecting boss i6, preferably of more or less rectangular transverse section, and which is designed to fit with a sliding fit within a downwardly directed socket ll formed. in the roof 7 of the posterior portion 7. This socket ll, as shown in Fig. 3, has a fiat bottom wall and is open at its rear. Preferably a spring tongue i8 is fixed at its rear end to the under side of the roof l and has its free forward end parallel to the bottom wall of the socket, so that when the lug or boss I6 is slid between the bottom wall of the socket and the spring tongue, it will be retained in place by the frictional pressure of the tongue. In this way the anterior portion I2 may be united to the posterior portion but with provision for adjustment of the anterior portion forwardly and rearwardly relative to the posterior portion.

As described in the above-noted application, the part l2 with its complement of anterior teeth removably secured in place by means of wax, constitutes a very convenient and effective way of shipping sets of anterior teeth from the manufacturer to the dentist. The dentist may provide himself with a large number of sets of these anterior teeth, and may readily associate any selected one of such sets (without removing the teeth from the holder) with the posterior impression tray I. The procedure in making a permanent denture by the use of this adjustable tray, is substantially as above described, the posterior portion being provided with teeth H set in wax, and the anterior portion being selected from an available supply of such holders, thus facilitating the making up of the trial plate, since in many instances it may not be necessary to rearrange the anterior teeth within the portion l2 of the impression tray.

As illustrated in Fig. 3, the posterior impression tray is furnished with a simple form of spring socket inwhich the boss l6 may slide with more or less friction. In Fig. 5, a modified arrangement is shown wherein the posterior portion 1 of the tray has an integral, forwardly directed tongue Ifi which is clamped against the upper surface of the boss [6 of the anterior portion I2 by means of a simple screw clamp I 1*. As shown in Fig. 6, the posterior tray 1 may be furnished with a downwardly directed screwthreaded stud ll which passes through an opening ll in a bracket i8 the bracket being secured to the stud ll by means of a nut, or in any other desired manner. This bracket Id (Fig. 6*) has a forward portion I8 provided with a rectangular channel l8 designed to receive the lug it of the anterior tray member 12. A clamping screw IS is received in a threaded opening in the bracket l8 and may be screwed up to clamp the boss it in adjusted position. With this arrangement the anterior portion l2 may be accurately adjusted and firmly secured in adjusted position.

Instead of making the tray so that it may be adjusted in front-to-rear depth, it may be preferred to make the tray so that it may be adjusted widthwise. Thus, as illustrated in Fig. 7, the tray l9 comprises the independent lateral portions and 2!, each having a gum-receiving groove 22 and 23, respectively at its impression side, and

having a tooth-receiving groove 24 and 25, respectively, at its opposite side, the labial walls 26 and 2? of said grooves being designed to simulate gum tissue. These grooves 24 and are intended to receive a body of wax in which the gingival ends of the teeth are disposed. The parts 20 and 2| are furnished with downwardly directed lugs 28 and 29, which are internally screw-threaded with right and left-hand threads, respectively, and these screw-threaded openings receive the opposite ends of an adjusting screw 30 having threads of opposite pitch at its opposite end portions. By turning this screw, the width of the impression tray may be varied. When using any of these multiple-part trays, the joint between the parts (after adjustment) may be sealed with wax before the impression is taken.

The tray above described is for use in making an upper denture, but it is to be understood that the invention is equally useful when embodied in a tray for making a lower denture. Such a tray is illustrated in Figs. 9 and 10, wherein the tray l which is of U-shape to conform to the lower gum ridge, is provided with a channel 2 in its lower or impression surface for the reception of the gum ridge, and with a second channel 4 in its opposite surface for the reception of the gingival ends of lower teeth, the labial wall 5 of this channel 4 being designed to simulate gum tissue and having the upwardly directed cusps 6 designed partially to embrace the necks of teeth of the lower set. The manner of use of this lower tray in making a permanent denture is the same as that above described, and results in the formation of a denture in which the teeth are arranged to provide the best possible appearance and accuracy of function.

While the trays above described may be made, as already suggested, of a material which is substantially rigid, such as metal, vulcanite, or the like, a preferred construction and one which has substantial advantages over that already described in detail contemplates the making of the tray from a substance which, although substantially rigid and shape-retaining at room temperatures, becomes mouldable and pliable at temperatures which are not injurious to the mouth tissues. It has been found that the mouth is not injured by a temperature as high as 150 F., and that a temperature of 140 is not at all uncomfortable to the patient. Certain of the synthetic resins, as well as certain cellulose derivatives, become sufficiently pliable at temperatures not ex- Ceeding 150, so that they may be moulded to conform fairly closely to the oral surfaces by under other than heat treatment, for example, by

solvents, may be employed.

In proceeding to make a permanent denture by the use of an impression tray formed of such mouldable plastic material, the tray is first prepared by substantially the same methods as might it be employed in making a tray of the usual permanently rigid materials. Ordinarily a substantial size range of these plastic trays will be provided, although the range need not be as great as when the trays are of rigid material.

aving prepared such plastic trays, a dentist then selects the tray which appears most nearly to approximate the size and contour of the oral surface against which the denture is to fit, and having warmed this tray to the plastic temperature, he introduces it into the patients mouth, and by digital pressure conforms it as closely as may be to the oral surfaces. Although the tray is mouldable, it does not have the characteristics of a free fluid, and as it has substantial thickness, it is not necessary by such pressure against its exposed surface to conform it absolutely and accurately to the oral surface, although it may be made to conform with a much greater degree of accuracy than does the usual rigid impression tray.

After this tray ha cooled enough to retain its shape, it is removed from the mouth and a body of dental wax or similar material is disposed within the tooth-receiving cavity, The dentist then arranges a set of teeth within this body of wax in the same way as above described, and returns the tray with its completment of teeth to the mouth. The teeth are now tested in the mouth for appearance, arrangement and bite, and are rearranged and reset until optimum results are secured. The tray is now again removed from the mouth and a thin layer of very plastic impression material, such as above referred to, is spread over the impression surface of the tray and the tray is again placed in the mouth and pressed against the oral surface and held while the impression layer is setting. Since this type of tray with its thin layer of impression material need be no thicker than the intended denture, and since it contains the teeth all set up in proper arrangement, it may at once be flasked, invested and processed. Thus, the teeth'become permanently fixed in the denture in th exact arrangement and setting which has been determined by the use of the impression tray having the teeth mounted therein.

By the use of this mouldable tray, which may be so closely conformed to the oral surfaces before any impression material is used, the operation of taking the impression is greatly facilitated, since only a relatively small quantity of the impression material is used and this relatively thin layer is supported at all points by the rigid tray which lies immediately behind the impression layer. There is thus little opportunity for the impression material to flow sidewise, or for the tray to rock while the impression is being taken; there is but little surplus of the impression material to escape into the patients mouth and cause annoyance; and the quantity or impression material is so small and it is so closely confined that there is very little spill over.

It will be observed that by the use of all of the various forms of tray above described, Whether rigid or mouldable, it is possible at an early stage in the operation to set the teeth in the permanent arrangement which they are to occupy in the denture when complete, a possibility which prior procedures have not contemplated. The advantages of this procedure are manifest, both from the standpoint of facility in making the denture and from the standpoint of the patient, who may.

be assured by such method of obtaining a substantially perfect denture with a minimum of trouble and discomfort. While I have for convenience considered the procedure as if the posteriorsection of the tray were received empty it would not depart from the spirit of this invention to ship the tray with either wax or teeth or both mounted thereon.

While certain desirable embodiments of the invention have hereinabove been described, it is to be understood thatthe invention is not necessarily limited to these precise embodiments but is to be regarded as broadly inclusive of any and all modifications thereof such as fall within the scope of the appended claims.

I claim:

1. A dental impression tray of a material which is rigid and shape-retaining at room temperatures but which is pliable at a temperature approximating 140 F. having at one side a surface designed to support a layer of plastic impression material, said surface being contoured approximately to fit a surface of the oral cavity, the opposite side of the tray having provision for removably attaching artificial teeth thereto without injury to or distortion of the tray proper.

2. A dental impression tray useful in taking an impression of a surface of the oral cavity, said tray of a material which is rigid and shape-retaining at room temperature, said tray having an impression surface, a gum-simulating portion, a cavity for the reception of the gingival portions of artificial teeth, and a plastic within said cavity operative to hold teeth therein, said plastic being separate from the tray proper and of a nature such that when slightly warmed it softens sufficiently to permit the teeth to be relatively moved for adjustment or to be removed and replaced without injury to the tray proper.

3. A dental impression tray of a material which is rigid and shape-retaining at room temperature but which is pliable at a temperature approximately 140 F., said tray having an impression surface at one side thereof shaped substantially to conform to a gum ridge and having in its other side a cavity designed to receive artificial teeth, and plastic means within said cavity removably securing said teeth in place, said plastic being independent of the tray proper and being of a nature such that it softens when slightly warmed.

4. A dental impression tray having at one side an impression surface defining the walls of a marginal channel designed to receive the gum ridge, the material of the tray being substantially rigid and shape-retaining at normal room temperatures but becoming mouldable at a temperature not exceeding 150 F. so that the tray may be approximately conformed to the gum ridge by digital pressure, the opposite side of the tray having a marginal channel for the reception of the gingival ends of artificial teeth, and toothretaining plastic, difierent in character from the tray proper, within said channel, said tooth-retaining plastic softening when slightly warmed.

5. A dental impression tray comprising separable posterior and anterior parts, each of said parts having provision for removably securing artificial teeth therein, and means removably uniting said parts. ,7

6. A dental impression traylgomprising separable posterior and anterioripartsrand clamping means operative adjustablytorunite said parts thereby to vary the length of the -tray, one, at least, of said parts haVing therein a cavity for the reception of artificial teeth, and means operative removably to secure teeth in. each of said respective cavities.

7. A dental impression tray comprising relatively movable lateral parts, each of said parts having at one side thereof an impression surface defining a channel for the reception of a portion of the gum ridge, each of said parts having at its opposite side a channel for the reception of the gingival portions of artificial teeth, means operative removably to hold teeth in said latter channels, and means operative adjustably to unite said lateral parts of the tray thereby to vary the effective size of the tray.

8. That method of making a denture which comprises as steps, providing an impression tray having an impression-taking face and a toothreceiving portion, applying a layer of plastic impression material to the impression surface of the tray, positioning the tray in the mouth, and taking the impression, removing the impression from the mouth, mounting the teeth, which have been tentatively selected for the case, on the tooth-receiving portion of the tray, and then replacing the tray carrying the impression and the teeth in the mouth and making any desired adjustments of the said teeth.

9. Method of making dentures which comprises as steps preparing a trial plate by first providing a rigid support having an impression surface which substantially, but which does not exactly,

conform to the contour of an oral surface, the 5 opposite side of. the support having therein a tooth-receiving cavity, disposing a low melting point waxy material in said cavity, embedding the gingival ends of said teeth in said waxy material, placing the support in the patients mouth, adjusting, rearranging and/or replacing the teeth until, by test, the teeth have the desired functional accuracy and appearance, thereafter making a first impression by applying a layer of plastic impression material to the impression surface of the support, pressing said layer against said oral surface and retaining it in place until said layer has set, and removing the trial plate thus prepared from the mouth.

10. Method of making dentures which comprises as steps providing an impression tray comprising means for temporarily securing teeth thereto, the tray being of a material which is mouldable at a temperature not exceeding 150 F., causing the tray to become mouldable, approximately conforming the tray to the contour of the gum ridge by digital pressure, permitting the tray to cool and harden, removing the tray from the mouth, temporarily mounting artificial teeth in the tray, arranging the tray with its complement of teeth within the mouth, adjusting the teeth to obtain the desired appearance and bite, applying an impression layer to the contoured surface of the tray, positioning the tray within the mouth and pressing it into place, permitting the impression layer to set, removing the tray with the adjusted teeth thereon as a unit from the mouth. 7

11. A dental tray having substantially U- shaped channels at its upper and under sides respectively, said channels substantially registering with one another and being separated by a thin web of the tray-forming material, one of said channels being shaped approximately to conform to the contour of the gum ridge and being designed for the reception of impression material and the other of said channels being designed to receive a body of plastic tooth-retaining substance, the labial wall of said latter channel being shaped to resemble gum tissue.

12. A dental tray of normally rigid shape-retaining material comprising a roof portion, and means cooperating therewith to define an upwardly open, marginal gum-receiving channel, the tray also comprising parts defining a downwardly open tooth-receiving channel, said channels substantially registering with each other. the labial wall of the tooth-receiving channel being contoured to resemble gum tissue.

SIMON MYERSON. 

